The present invention relates broadly to camera systems, and in particular to a scan corrected vidicon camera.
In the present art, a major limitation in the use of vidicon cameras is the problem of image distortion. Techniques have been advanced to correct the errors in the vertical scan, however, these techniques require the use of a minicomputer which greatly increases the cost of such systems.
In general, such systems operate to automatically generate a digital correction over a 32.times.32 correction array and only the vertical scan errors were corrected. There were no provisions to provide corrections for the horizontal scan. The scan correction is achieved by illuminating the target with an array of parallel lines of light, one for each scan line in the vidicon raster. This requires that a transmission diffraction grating be accurately imaged to the vidicon target. As the vidicon electron beam scans the raster, the output video signal is a function of the vertical scan error. The alignment of the scan to the illuminated line yields the maximum video output. A correction value for each sub-raster areas is obtained by perturbing the vertical scan in this region, until the video output is peaked. The computer methodically works its way over the raster area until the moire fringes resulting from vertical scan errors are corrected to yield one white fringe over the entire raster. While this method is quite effective, it requires a large array of expensive peripheral equipment and it requires that a high resolution grating be imaged to the vidicon target during correction.